This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Streptococcus pneumoniae is a leading cause of meningitis, pneumonia, and severe invasive pneumococcal disease (IPD)) in infants and young children throughout the world. The 7-valent pneumococcal conjugate vaccine (7vPnC, Prevnar/Prevenar a) was demonstrated to be highly immunogenic and effective against IPD and otitis media in infants and young children. Depending on geographic region the percentage of IPD cases caused by one of the Prevnar serotypes ranges from 40% to 90%. The 13-valent pneumococcal conjugate vaccine (13vPnC) would significantly expand the percentage of IPD cases that are vaccine preventable beyond that of Prevnar. Licensure of 13vPnC will be based on showing immunologic noninferiority to 7vPnC. That assessment will be made in separate trials in the United States and Europe. The current study will evaluate the safety, tolerability, and immunogenicity of 3 lots of 13vPnC and compare the immune response to each of the lots when given in a 2-, 4-, and 6-month infant series followed by a toddler dose at the age of 12 months. A group of subjects will also receive 7vPnC to provide additional comparative safety information, Responses to the following antigens in Pediarix will be assessed: tetanus;poliovirus types 1, 2, and 3;and hepatitis B. This is a parallel-group, randomized, active-controlled, double-blind, multicenter trial in which subjects will be randomized in a 2:2:2:1 ratio to receive 13vPnC pilot scale lot 1, 13vPnC pilot scale lot 2, 13vPnC manufacturing scale lot, or 7vPnC. The results of the study will shed light on the potential of this vaccine.